Leveling system for lift device

ABSTRACT

A lift device includes a chassis, a rear leveling assembly coupled to a rear end of the chassis, and a front leveling assembly coupled to a front end of the chassis. The rear leveling assembly includes a first rear actuator and a second rear actuator. The first rear actuator and the second rear actuator are selectively engageable to facilitate providing active control of a rear pitch adjustment and a rear roll adjustment of the rear leveling assembly. The front leveling assembly includes a first front actuator and a second front actuator. The first front actuator and the second front actuator are (i) selectively fluidly couplable to facilitate providing passive control of a front pitch adjustment and a front roll adjustment of the front leveling assembly and (ii) selectively fluidly decouplable to facilitate providing active control of the front pitch adjustment and the front roll adjustment of the front leveling assembly.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/482,601, filed Apr. 7, 2017, which claims the benefit of U.S.Provisional Patent Application No. 62/320,280, filed Apr. 8, 2016, bothof which are incorporated herein by reference in their entireties.

BACKGROUND

Traditional boom lifts may include a chassis, a turntable coupled to thechassis, and a boom assembly. The boom assembly may include one or moreboom sections that are pivotally connected. A lift cylinder elevates oneof the boom sections relative to the turntable and/or another one of theboom sections, thereby elevating an implement (e.g., work platform,forks, etc.) that is coupled to the boom assembly.

SUMMARY

One embodiment relates to a lift device. The lift device includes achassis, a rear leveling assembly coupled to a rear end of the chassis,and a front leveling assembly coupled to a front end of the chassis. Therear leveling assembly includes a first rear actuator and a second rearactuator. The first rear actuator and the second rear actuator areselectively engageable to facilitate providing active control of a rearpitch adjustment and a rear roll adjustment of the rear levelingassembly. The front leveling assembly includes a first front actuatorand a second front actuator. The first front actuator and the secondfront actuator are (i) selectively fluidly couplable to facilitateproviding passive control of a front pitch adjustment and a front rolladjustment of the front leveling assembly and (ii) selectively fluidlydecouplable to facilitate providing active control of the front pitchadjustment and the front roll adjustment of the front leveling assembly.

Another embodiment relates to a leveling system for a lift device. Theleveling system includes a first leveling assembly and a second levelingassembly. The first leveling assembly is configured to pivotally coupleto a first end of a chassis of the lift device. The first levelingassembly includes a first actuator and a second actuator. The secondleveling assembly is configured to pivotally couple to an opposingsecond end of the chassis of the lift device. The second levelingassembly includes a third actuator and a fourth actuator. The firstactuator and the second actuator are configured to be passivelycontrolled during a first mode of operation of the lift device. Thefirst actuator and the second actuator are configured to be activelycontrolled during a second mode of operation of the lift device. Thethird actuator and the fourth actuator are configured to be activelycontrolled during at least one of the first mode of operation and thesecond mode of operation of the lift device.

Another embodiment relates to a leveling system for a vehicle. Theleveling system includes a first leveling assembly and a second levelingassembly. The first leveling assembly is configured to pivotally coupleto a first end of a chassis of the vehicle. The first leveling assemblyis configured to be (i) passively controlled to provide a passive pitchadjustment and a passive roll adjustment of the first leveling assemblyduring a first mode of operation, and (ii) actively controlled toprovide an active pitch adjustment and an active roll adjustment of thefirst leveling assembly during a second mode of operation. The secondleveling assembly is configured to pivotally couple to an opposingsecond end of the chassis. The second leveling assembly is configured tobe actively controlled to provide an active pitch adjustment and anactive roll adjustment of the second leveling assembly during at leastone of the first mode of operation and the second mode of operation.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be generally recited in theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the followingdetailed description taken in conjunction with the accompanying drawingswherein like reference numerals refer to like elements, in which:

FIG. 1 is a perspective view of a lift device having a chassis, aleveling system, and a turntable, according to an exemplary embodiment;

FIG. 2 is a detailed perspective view of the chassis and the turntableof the lift device of FIG. 1, according to an exemplary embodiment;

FIGS. 3 and 4 are detailed perspective views of the chassis and theleveling system of the lift device of FIG. 1, according to an exemplaryembodiment;

FIG. 5 is a side view of the chassis and the leveling system of the liftdevice of FIG. 1, according to an exemplary embodiment;

FIG. 6 is a front view of the chassis and the leveling system of thelift device of FIG. 1, according to an exemplary embodiment;

FIG. 7 is a perspective cross-sectional view of the leveling system anda steering system of the lift device of FIG. 1, according to anexemplary embodiment;

FIGS. 8-10 are various views of the chassis and the leveling system ofthe lift device of FIG. 1 in a pivoted orientation, according to anexemplary embodiment;

FIG. 11 is a schematic diagram of an actuator circuit for the levelingsystem of the lift device of FIG. 1, according to an exemplaryembodiment;

FIG. 12 is a schematic block diagram of a control system of the liftdevice of FIG. 1, according to an exemplary embodiment;

FIGS. 13-20 are illustrations of various modes of operation of the liftdevice of FIG. 1, according to various exemplary embodiments; and

FIG. 21 is a flow diagram of a method for controlling a lift deviceaccording to various modes of operation, according to an exemplaryembodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

According to an exemplary embodiment, a lift device includes a levelingsystem configured to maintain a chassis of the lift device levelrelative to gravity (e.g., flat, horizontal, etc.) while stationaryand/or while moving (e.g., being driven, etc.). According to anexemplary embodiment, the leveling system operates as a semi-independentsuspension system for the lift device. The leveling system may include afront leveling assembly pivotally coupled to a front end of the chassisand a rear leveling assembly pivotally coupled to a rear end of thechassis. The terms “front,” “rear,” “left,” and “right” as used hereinare relative terms to provide reference and not necessarily intended tobe limiting. According to an exemplary embodiment, the leveling systemimproves the traction capabilities of the lift device by distributingloads between the tractive elements of the lift device while on unevenand/or sloped terrain. The leveling system may facilitate operating thelift device on larger slopes more effectively than traditional liftdevices. According to an exemplary embodiment, the front levelingassembly and the rear leveling assembly are configured to facilitateproviding two degrees of movement (e.g., pitch and roll, etc.). The liftdevice is configured to operate in various modes of operation (e.g., aboom operation mode, a transport mode, a driving mode, a calibrationmode, etc.), according to an exemplary embodiment. At least one of thefront leveling assembly and the rear leveling assembly may be activelycontrolled by a controller based on the mode of operation of the liftdevice. By way of example, the rear leveling assembly may be activelycontrolled by the controller and the front leveling assembly may bypassively operated during a first mode of operation (e.g., a drivingmode, etc.) of the lift device. By way of another example, the frontleveling assembly and the rear leveling assembly may both be activelycontrolled by the controller during a second mode of operation (e.g., aboom operation mode, etc.) of the lift device. “Active control” refersto engaging valves, pumps, etc. with a processing circuit or controllerto selectively vary the extension, retraction, etc. of an actuator(e.g., a hydraulic cylinder, etc.). “Passive control” refers to actuatorextension, retraction, etc. that is permitted but not regulated using aprocessing circuit or controller.

According to the exemplary embodiment shown in FIGS. 1-10, a lift device(e.g., an aerial work platform, a telehandler, a boom lift, a scissorlift, etc.), shown as lift device 10, includes a chassis, shown as liftbase 12. In other embodiments, the lift device 10 is another type ofvehicle (e.g., a fire apparatus, a military vehicle, an airport rescuefire fighting (“ARFF”) truck, a boom truck, a refuse vehicle, a forklift, etc.). As shown in FIGS. 1 and 2, the lift base 12 supports arotatable structure, shown as turntable 14, and a boom assembly, shownas boom 40. According to an exemplary embodiment, the turntable 14 isrotatable relative to the lift base 12. According to an exemplaryembodiment, the turntable 14 includes a counterweight positioned at arear of the turntable 14. In other embodiments, the counterweight isotherwise positioned and/or at least a portion of the weight thereof isotherwise distributed throughout the lift device 10 (e.g., on the liftbase 12, on a portion of the boom 40, etc.). As shown in FIGS. 1-10, afirst end, shown as front end 20, of the lift base 12 is supported by afirst plurality of tractive elements, shown as front tractive elements16, and an opposing second end, shown as rear end 30, of the lift base12 is supported by a second plurality of tractive elements, shown asrear tractive elements 18. According to the exemplary embodiment shownin FIGS. 1-10, the front tractive elements 16 and the rear tractiveelements 18 include wheels. In other embodiments, the front tractiveelements 16 and/or the rear tractive elements 18 include a trackelement.

As shown in FIG. 1, the boom 40 includes a first boom section, shown aslower boom 50, and a second boom section, shown as upper boom 70. Inother embodiments, the boom 40 includes a different number and/orarrangement of boom sections (e.g., one, three, etc.). According to anexemplary embodiment, the boom 40 is an articulating boom assembly. Inone embodiment, the upper boom 70 is shorter in length than lower boom50. In other embodiments, the upper boom 70 is longer in length than thelower boom 50. According to another exemplary embodiment, the boom 40 isa telescopic, articulating boom assembly. By way of example, the upperboom 70 and/or the lower boom 50 may include a plurality of telescopingboom sections that are configured to extend and retract along alongitudinal centerline thereof to selectively increase and decrease alength of the boom 40.

As shown in FIG. 1, the lower boom 50 has a first end (e.g., lower end,etc.), shown as base end 52, and an opposing second end, shown asintermediate end 54. According to an exemplary embodiment, the base end52 of the lower boom 50 is pivotally coupled (e.g., pinned, etc.) to theturntable 14 at a joint, shown as lower boom pivot 56. As shown in FIG.1, the boom 40 includes a first actuator (e.g., pneumatic cylinder,electric actuator, hydraulic cylinder, etc.), shown as lower liftcylinder 60. The lower lift cylinder 60 has a first end coupled to theturntable 14 and an opposing second end coupled to the lower boom 50.According to an exemplary embodiment, the lower lift cylinder 60 ispositioned to raise and lower the lower boom 50 relative to theturntable 14 about the lower boom pivot 56.

As shown in FIG. 1, the upper boom 70 has a first end, shown asintermediate end 72, and an opposing second end, shown as implement end74. According to an exemplary embodiment, the intermediate end 72 of theupper boom 70 is pivotally coupled (e.g., pinned, etc.) to theintermediate end 54 of the lower boom 50 at a joint, shown as upper boompivot 76. As shown in FIG. 1, the boom 40 includes an implement, shownas platform assembly 92, coupled to the implement end 74 of the upperboom 70 with an extension arm, shown as jib arm 90. In some embodiments,the jib arm 90 is configured to facilitate pivoting the platformassembly 92 about a lateral axis (e.g., pivot the platform assembly 92up and down, etc.). In some embodiments, the jib arm 90 is configured tofacilitate pivoting the platform assembly 92 about a vertical axis(e.g., pivot the platform assembly 92 left and right, etc.). In someembodiments, the jib arm 90 is configured to facilitate extending andretracting the platform assembly 92 relative to the implement end 74 ofthe upper boom 70. As shown in FIG. 1, the boom 40 includes a secondactuator (e.g., pneumatic cylinder, electric actuator, hydrauliccylinder, etc.), shown as upper lift cylinder 80. According to anexemplary embodiment, the upper lift cylinder 80 is positioned toactuate (e.g., lift, rotate, elevate, etc.) the upper boom 70 and theplatform assembly 92 relative to the lower boom 50 about the upper boompivot 76.

According to an exemplary embodiment, the platform assembly 92 is astructure that is particularly configured to support one or moreworkers. In some embodiments, the platform assembly 92 includes anaccessory or tool configured for use by a worker. Such tools may includepneumatic tools (e.g., impact wrench, airbrush, nail gun, ratchet,etc.), plasma cutters, welders, spotlights, etc. In some embodiments,the platform assembly 92 includes a control panel to control operationof the lift device 10 (e.g., the turntable 14, the boom 40, etc.) fromthe platform assembly 92. In other embodiments, the platform assembly 92includes or is replaced with an accessory and/or tool (e.g., forkliftforks, etc.).

As shown in FIGS. 1-10, the lift device 10 includes a chassis levelingassembly, shown as leveling system 100. According to an exemplaryembodiment, the leveling system 100 is configured to facilitatemaintaining the lift base 12, the turntable 14, and/or the platformassembly 92 of the lift device 10 level relative to gravity (e.g., whilestationary, while being driven on uneven and/or sloped ground, whileoperating the boom 40, etc.). As shown in FIGS. 1-10, the levelingsystem 100 includes a first leveling assembly, shown as front levelingassembly 110, pivotally coupled to the front end 20 of the lift base 12and a second leveling assembly, shown as rear leveling assembly 120,pivotally coupled to the rear end 30 of the lift base 12. According toan exemplary embodiment, the front leveling assembly 110 and the rearleveling assembly 120 operate as a semi-independent suspension systemfor the lift device 10. Such a semi-independent suspension operation mayfacilitate providing two degrees of movement (e.g., pitch and roll,etc.) with each of the front leveling assembly 110 and the rear levelingassembly 120.

The lift device 10 may provide various features and/or performancecharacteristics that are advantageous for lift device operation. Suchadvantages may include: (i) providing a platform capacity of up to 600pounds or more, (ii) providing a platform height of up to 46.5 feet ormore, (iii) providing a horizontal reach of up to 39 feet or more, (iv)providing a platform rotation of up to 180 degrees or more, (v)providing a boom swing of up to 360 degrees, (vi) providing a drivespeed of up to 4.5 miles per hour or more, (vii) providing agradeability of up to 45 degrees or more, (viii) providing a turningradius of 16 feet or less, (ix) providing a variable ground clearancebetween less than 6 inches to more than 22 inches, and/or (x) providingup to +/− 10 degrees or more of chassis pitch and roll, among stillother advantages.

As shown in FIGS. 2-10, the front leveling assembly 110 includes a firstcarrier arm, shown as front trailing arm 130; a first axle, shown asfront axle 150; a first front actuator, shown as front right actuator170; and a second front actuator, shown as front left actuator 180.According to an exemplary embodiment, the front right actuator 170 andthe front left actuator 180 each include a hydraulic cylinder. In otherembodiments, the front right actuator 170 and/or the front left actuator180 include another type of actuator (e.g., a pneumatic cylinder, anelectric actuator, etc.). As shown in FIGS. 3, 5, 7, and 9, the fronttrailing arm 130 has a first portion, shown as base 131, positioned at afirst end, shown as chassis end 132, of the front trailing arm 130. Asshown in FIGS. 2-4 and 6-10, the front trailing arm 130 has a secondportion, shown as projection 133, positioned at an opposing second end,shown as axle end 134, of the front trailing arm 130. As shown in FIGS.3, 4, and 7-9, the front trailing arm 130 has a third portion, shown astransition 135, extending between the base 131 and the projection 133.As shown in FIGS. 3, 5, and 7, the base 131 defines a pivot interface atthe chassis end 132 of the front trailing arm 130 that pivotally couplesto the front end 20 of the lift base 12 at a pair of pivot pointspositioned at a bottom end of the front end 20 of the lift base 12,shown as lower right pivot 26 and lower left pivot 28. Such a pivotalcoupling between the front end 20 of the lift base 12 and the fronttrailing arm 130 may facilitate a pitch adjustment operation of thefront leveling assembly 110 (e.g., pivoting of the front trailing arm130 about a lateral axis extending through the lower right pivot 26 andthe lower left pivot 28, etc.).

According to the exemplary embodiment shown in FIGS. 3,4, and 7-9, thetransition 135 extends from the base 131 to the projection 133 at anangle such that the projection 133 is elevated relative to the base 131.The front trailing arm 130 may thereby have a ramped or sloped profile(e.g., an elongated S-shape, an elongated Z-shape, etc.). In someembodiments, the base 131 and the projection 133 are parallel with eachother (e.g., planes defined by the base 131 and the projection 133 maybe parallel, etc.). As shown in FIG. 7, the front trailing arm 130 has adual-plate construction such that the front trailing arm 130 includes afirst, upper plate and a second, lower plate spaced from the first,upper plate (e.g., a space or gap is formed therebetween, etc.). Inother embodiments, the front trailing arm 130 has a single plateconstruction and/or has a solid structure.

As shown in FIGS. 3-7, the front axle 150 has a first end, shown asright end 152, and an opposing second end, shown as left end 154. Afirst front tractive element 16 is coupled to the right end 152 of thefront axle 150, and a second front tractive element 16 is coupled to theleft end 154 of the front axle 150. As shown in FIG. 7, the front axle150 includes a coupler, shown as front axle pivot interface 156,positioned to engage a corresponding coupler, shown as front trailingarm pivot interface 136, defined by the projection 133 and positioned atthe axle end 134 of the front trailing arm 130. As shown in FIG. 7, thefront axle pivot interface 156 and the front trailing arm pivotinterface 136 are configured to interengage and cooperatively receive afastener, shown as pin 158. According to an exemplary embodiment, thepin 158 pivotally couples the front axle 150 to the axle end 134 of thefront trailing arm 130. The pivotal joint between the front trailing arm130 and the front axle 150 may facilitate a roll adjustment operation ofthe front leveling assembly 110 about the pin 158 (e.g., pivoting of thefront axle 150 about a central longitudinal axis of the lift device 10,etc.).

As shown in FIGS. 2-4 and 6, a first end (e.g., an upper end, etc.) ofthe front right actuator 170 is pivotally coupled to the front end 20 ofthe lift base 12 at a pivot point, shown as upper right pivot 22.According to an exemplary embodiment, an opposing second end (e.g., alower end, etc.) of the front right actuator 170 is pivotally coupled toa corresponding pivot point positioned along the front axle 150 (e.g.,proximate the right end 152 thereof, etc.). As shown in FIGS. 2-6, afirst end (e.g., an upper end, etc.) of the front left actuator 180 ispivotally coupled to the front end 20 of the lift base 12 at a pivotpoint, shown as upper left pivot 24. According to an exemplaryembodiment, an opposing second end (e.g., a lower end, etc.) of thefront left actuator 180 is pivotally coupled to a corresponding pivotpoint positioned along the front axle 150 (e.g., proximate the left end154 thereof, etc.). Such a pivotal coupling of (i) the front rightactuator 170 between the front end 20 of the lift base 12 and the frontaxle 150 and (ii) the front left actuator 180 between the front end 20of the lift base 12 and the front axle 150 may facilitate activelyand/or passively providing the pitch and/or roll adjustment operationsof the front leveling assembly 110 (e.g., pivoting of the front trailingarm 130 about a lateral axis extending through the lower right pivot 26and the lower left pivot 28, pivoting of the front axle 150 about acentral longitudinal axis of the lift device 10, etc.).

As shown in FIGS. 2-5, 8, and 9, the rear leveling assembly 120 includesa second carrier arm, shown as rear trailing arm 140; a second axle,shown as rear axle 160; a first rear actuator, shown as rear rightactuator 190; and a second rear actuator, shown as rear left actuator200. According to an exemplary embodiment, the rear right actuator 190and the rear left actuator 200 each include a hydraulic cylinder. Inother embodiments, the rear right actuator 190 and/or the rear leftactuator 200 include another type of actuator (e.g., a pneumaticcylinder, an electric actuator, etc.). As shown in FIGS. 2, 3, and 5,the rear trailing arm 140 has a first portion, shown as base 141,positioned at a first end, shown as chassis end 142, of the reartrailing arm 140. As shown in FIGS. 2-4, 8, and 9, the rear trailing arm140 has a second portion, shown as projection 143, positioned at anopposing second end, shown as axle end 144, of the rear trailing arm140. As shown in FIGS. 2 and 3, the rear trailing arm 140 has a thirdportion, shown as transition 145, extending between the base 141 and theprojection 143. According to an exemplary embodiment, the base 141defines a pivot interface at the chassis end 142 of the rear trailingarm 140 that pivotally couples to the rear end 30 of the lift base 12 ata pair of lower pivot points positioned at a bottom end of the rear end30 of the lift base 12 (e.g., similar to the base 131 of the fronttrailing arm 130 at the lower right pivot 26 and the lower left pivot28, etc.). Such a pivotal coupling between the rear end 30 of the liftbase 12 and the rear trailing arm 140 may facilitate a pitch adjustmentoperation of the rear leveling assembly 120 (e.g., pivoting of the reartrailing arm 140 about a lateral axis extending through the pair oflower pivot points of the rear end 30 of the lift base 12, etc.).

According to the exemplary embodiment shown in FIGS. 2 and 3, thetransition 145 extends from the base 141 to the projection 143 at anangle such that the projection 143 is elevated relative to the base 141.The rear trailing arm 140 may thereby have a ramped or sloped profile(e.g., an elongated S-shape, an elongated Z-shape, etc.). In someembodiments, the base 141 and the projection 143 are parallel with eachother (e.g., planes defined by the base 141 and the projection 143 maybe parallel, etc.). According to an exemplary embodiment, the reartrailing arm 140 has a dual-plate construction such that the reartrailing arm 140 includes a first, upper plate and a second, lower platespaced from the first, upper plate (e.g., a space or gap is formedtherebetween, etc.). In other embodiments, the rear trailing arm 140 hasa single plate construction and/or has a solid structure.

As shown in FIGS. 3-5, the rear axle 160 has a first end, shown as rightend 162, and an opposing second end, shown as left end 164. A first reartractive element 18 is coupled to the right end 162 of the rear axle 160and a second rear tractive element 18 is coupled to the left end 164 ofthe rear axle 160. According to an exemplary embodiment, the rear axle160 includes a rear axle pivot interface (e.g., similar to the frontaxle pivot interface 156 of the front axle 150, etc.) positioned toengage a corresponding rear trailing arm pivot interface defined by theprojection 143 and positioned at the axle end 144 of the rear trailingarm 140 (e.g., similar to the front trailing arm pivot interface 136 ofthe front trailing arm 130, etc.). The rear axle pivot interface and therear trailing arm pivot interface are configured to interengage andcooperatively receive a fastener (e.g., similar to the pin 158, etc.) topivotally couple the rear axle 160 to the rear trailing arm 140,according to an exemplary embodiment. The pivotal joint between the reartrailing arm 140 and the rear axle 160 may facilitate a roll adjustmentoperation of the rear leveling assembly 120 (e.g., pivoting of the rearaxle 160 about a central longitudinal axis of the lift device 10, etc.).

As shown in FIGS. 2 and 3, a first end (e.g., an upper end, etc.) of therear right actuator 190 is pivotally coupled to the rear end 30 of thelift base 12 at a pivot point, shown as upper right pivot 32. Accordingto an exemplary embodiment, an opposing second end (e.g., a lower end,etc.) of the rear right actuator 190 is pivotally coupled to acorresponding pivot point positioned along the rear axle 160 (e.g.,proximate the right end 162 thereof, etc.). As shown in FIGS. 3-5, afirst end (e.g., an upper end, etc.) of the rear left actuator 200 ispivotally coupled to the rear end 30 of the lift base 12 at a pivotpoint, shown as upper left pivot 34. According to an exemplaryembodiment, an opposing second end (e.g., a lower end, etc.) of the rearleft actuator 200 is pivotally coupled to a corresponding pivot pointpositioned along the rear axle 160 (e.g., proximate the left end 164thereof, etc.). Such a pivotal coupling of (i) the rear right actuator190 between the rear end 30 of the lift base 12 and the rear axle 160and (ii) the rear left actuator 200 between the rear end 30 of the liftbase 12 and the rear axle 160 may facilitate actively and/or passivelyproviding the pitch and/or roll adjustment operations of the rearleveling assembly 120 (e.g., pivoting of the rear trailing arm 140 abouta lateral axis extending through the pair of lower pivot points of therear end 30 of the lift base 12, pivoting of the rear axle 160 about acentral longitudinal axis of the lift device 10, etc.).

As shown in FIGS. 3, 4, 6, and 7, the front axle 150 and the rear axle160 include a drive system, shown as drive system 220. The drive system220 includes actuators (e.g., pneumatic cylinders, electric actuators,hydraulic cylinders, etc.), shown as steering actuators 222, and drivers(e.g., electric actuators, motors, etc.), shown as drive actuators 224.As shown in FIGS. 3, 4, and 6, the front axle 150 includes a pair ofsteering actuators 222. Each steering actuator 222 may be positioned tofacilitate steering one of the front tractive elements 16 (e.g.,independent steering of each of the front tractive elements 16, etc.).According to an exemplary embodiment, the rear axle 160 includes a pairof steering actuators 222. Each steering actuator 222 may be positionedto facilitate steering one of the rear tractive elements 18 (e.g.,independent steering of each of the rear tractive elements 18, etc.). Inother embodiments, the front axle 150 and/or the rear axle 160 include asingle steering actuator 222 positioned to facilitate steering both ofthe front tractive elements 16 and/or both of the rear tractive elements18, respectively. As shown in FIGS. 3, 4, and 7, the front axle 150includes a pair of drive actuators 224. Each drive actuator 224 may bepositioned to facilitate driving one of the front tractive elements 16.According to an exemplary embodiment, the rear axle 160 includes a pairof drive actuators 224. Each drive actuator 224 may be positioned tofacilitate driving one of the rear tractive elements 18.

As shown in FIGS. 1 and 2, the lift device 10 includes an actuatorcircuit, shown as actuator circuit 300, and a control system, shown aslift device control system 400. According to an exemplary embodiment,the actuator circuit 300 includes a hydraulic circuit configured tofacilitate operating (e.g., driving the extension and/or retraction of,etc.) the front right actuator 170, the front left actuator 180, therear right actuator 190, the rear left actuator 200, the steeringactuators 222, and/or the drive actuators 224 (e.g., in embodimentswhere the actuators include hydraulic cylinders, etc.). In otherembodiments, the actuator circuit 300 includes an electric circuit(e.g., in embodiments where the actuators include electric actuators,etc.) and/or a pneumatic circuit (e.g., in embodiment where theactuators include pneumatic cylinders, etc.). According to an exemplaryembodiment, the lift device control system 400 is configured to controlthe operation of the actuator circuit 300 and thereby the front rightactuator 170, the front left actuator 180, the rear right actuator 190,the rear left actuator 200, the steering actuators 222, and/or the driveactuators 224 (e.g., the extension and/or retraction thereof, therelative motion between the front axle 150 and/or the rear axle 160 andthe lift base 12, the pitch and/or roll adjustment operations of thefront axle 150 and/or the rear axle 160, etc.).

According to the exemplary embodiment shown in FIG. 11, the actuatorcircuit 300 includes a pump, shown as pump 302, a fluid reservoir, shownas tank 304, and a low pressure source, shown as low pressure source306. The tank 304 is configured to supply the pump 302 with a fluid(e.g., hydraulic fluid, compressed air, etc.), which the pump 302provides at a high pressure throughout the actuator circuit 300. Asshown in FIG. 11, the actuator circuit 300 includes a high pressureline, shown as high pressure line 310, that includes a first highpressure line, shown as front high pressure line 320, and a second highpressure line, shown as rear high pressure line 330. The front highpressure line 320 includes a first front high pressure line, shown asfront right high pressure line 322, and a second front high pressureline, shown as front left high pressure line 324. As shown in FIG. 11,the front right high pressure line 322 fluidly couples the pump 302 to afirst front leveling module, shown as front right leveling module 172,associated with the front right actuator 170 and configured tofacilitate an extension and retraction operation of the front rightactuator 170. The front left high pressure line 324 fluidly couples thepump 302 to a second front leveling module, shown as front left levelingmodule 182, associated with the front left actuator 180 and configuredto facilitate an extension and retraction operation of the front leftactuator 180.

As shown in FIG. 11, the rear high pressure line 330 includes a firstrear high pressure line, shown as rear right high pressure line 332, anda second rear high pressure line, shown as rear left high pressure line334. The rear right high pressure line 332 fluidly couples the pump 302to a first rear leveling module, shown as rear right leveling module192, associated with the rear right actuator 190 and configured tofacilitate an extension and retraction operation of the rear rightactuator 190. The rear left high pressure line 334 fluidly couples thepump 302 to a second rear leveling module, shown as rear left levelingmodule 202, associated with the rear left actuator 200 and configured tofacilitate an extension and retraction operation of the rear leftactuator 200. According to an exemplary embodiment, the high pressureline 310 is positioned to facilitate providing high pressure fluid to afirst chamber, shown as first chamber 174, first chamber 184, firstchamber 194, and first chamber 204, of the front right actuator 170, thefront left actuator 180, the rear right actuator 190, and the rear leftactuator 200, respectively, to facilitate an extension operationthereof.

As shown in FIG. 11, the actuator circuit 300 includes a low pressureline including a first low pressure line, shown as front low pressureline 340, and a second low pressure line, shown as rear low pressureline 350. The front low pressure line 340 includes a first front lowpressure line, shown as front right low pressure line 342, and a secondfront low pressure line, shown as front left low pressure line 344. Asshown in FIG. 11, the front right low pressure line 342 and the frontleft low pressure line 344 are fluidly coupled to a third low pressureline, shown as third low pressure line 346. The third low pressure line346 fluidly couples the front right leveling module 172 and the frontleft leveling module 182 to a valve block, shown as valve block 370. Thevalve block 370 includes a valve, shown as valve 376, positioned toselectively fluidly couple the front low pressure line 340 to the lowpressure source 306 and/or a reservoir, shown as tank 308 (e.g., basedon a mode of operation of the lift device 10, etc.).

As shown in FIG. 11, the rear low pressure line 350 includes a firstrear low pressure line, shown as rear right low pressure line 352, and asecond rear low pressure line, shown as rear left low pressure line 354.As shown in FIG. 11, the rear right low pressure line 352 and the rearleft low pressure line 354 are fluidly coupled to a third low pressureline, shown as third low pressure line 356. The third low pressure line356 fluidly couples the rear right leveling module 192 and the rear leftleveling module 202 to the tank 308. According to an exemplaryembodiment, the front low pressure line 340 is positioned to facilitateproviding low pressure fluid to a second chamber, shown as secondchamber 176 and second chamber 186, of the front right actuator 170 andthe front left actuator 180, respectively, to facilitate a retractionoperation thereof. According to an exemplary embodiment, rear lowpressure line 350 is positioned to facilitate providing low pressurefluid to a second chamber, show as second chamber 196 and second chamber206, of the rear right actuator 190 and the rear left actuator 200,respectively, to facilitate a retraction operation thereof.

As shown in FIG. 11, the actuator circuit 300 includes an auxiliaryline, shown as auxiliary line 360. The auxiliary line 360 includes afirst auxiliary line, shown as front right auxiliary line 362, and asecond auxiliary line, shown as front left auxiliary line 364. The frontright auxiliary line 362 and the front left auxiliary line 364 arefluidly coupled to a third auxiliary line, shown as third auxiliary line366. The third auxiliary line 366 fluidly couples the front rightleveling module 172 and the front left leveling module 182 to the valveblock 370. According to an exemplary embodiment, the front low pressureline 340, the auxiliary line 360, and/or the valve block 370 arecooperatively engaged to operate the front right actuator 170 and thefront left actuator 180 according to a passive mode of operation (e.g.,based on the mode of operation of the lift device 10, a front levelingassembly free oscillation mode, etc.). By way of example, the passivemode of operation may be facilitated by activating (e.g., energizing,switching, opening, closing, etc.) valves (e.g., proportional valves,load holding valves, electro-magnetic valves, etc.) of the valve block370, shown as valve 372 and valve 374. Such activation may includeopening or closing one or more valves of the front right leveling module172, shown as actuator valves 178, and the front left leveling module182, shown as actuator valves 188. Such an operation may additionally oralternatively include activating (e.g., energizing, switching, opening,closing, etc.) a valve of the valve block 370, shown as valve 376, avalve of the front right leveling module 172, shown as actuator valve179, and/or a valve of the front left leveling module 182, shown asactuator valve 189. Such activation may thereby fluidly couple the firstchamber 174 and/or the second chamber 176 of the front right actuator170 to the first chamber 184 and/or the second chamber 186 of the frontleft actuator 180 to facilitate a fluid flow (e.g., a free fluid flow,etc.) therebetween (e.g., between the first chamber 174 and the secondchamber 186, between the second chamber 176 and the first chamber 184,etc.), as well as isolate the front right actuator 170 and the frontleft actuator 180 from the pump 302 (e.g., the front right actuator 170and the front left actuator 180 do not receive high pressure fluid fromthe pump 302 such that they are not actively controlled, but passivelycontrolled, etc.). According to an exemplary embodiment, the pressurefrom the low pressure source 306 is configured to ensure that the frontlow pressure line 340 remains pressurized (e.g., account for losses,etc.) through a valve, shown as check valve 378.

According to the exemplary embodiment shown in FIG. 12, the lift devicecontrol system 400 for the lift device 10 includes a controller 410. Inone embodiment, the controller 410 is configured to selectively engage,selectively disengage, control, and/or otherwise communicate withcomponents of the lift device 10 (e.g., actively control the componentsthereof, etc.). In some embodiments, the controller 410 is configured tofacilitate passively controlling at least some of the components to thelift device 10 (e.g., based on the mode of operation of the lift device10, the front leveling assembly 110, etc.). As shown in FIG. 12, thecontroller 410 is coupled to the turntable 14, the boom 40, the levelingsystem 100 (e.g., the leveling modules thereof, etc.), the drive system220 (e.g., the steering actuators 222, the drive actuators 224, etc.),the actuator circuit 300, various sensors including displacement sensors402, roll sensors 404, pitch sensors 406, and load sensors 408, and auser interface 440. In other embodiments, the controller 410 is coupledto more or fewer components. The controller 410 may be configured toactively control the pitch adjustment and/or the roll adjustment of atleast the one of (i) the front leveling assembly 110 (e.g., through theextension and/or retraction of the front right actuator 170 and/or thefront left actuator 180, etc.) and (ii) the rear leveling assembly 120(e.g., through the extension and/or retraction of the rear rightactuator 190 and/or the rear left actuator 200, etc.) to at leastimprove the orientation of the lift base 12, the turntable 14, and/orthe boom 40 relative to gravity (e.g., while driving the lift device 10,while operating the boom 40, in a longitudinal direction, in lateraldirection, etc.). By way of example, the controller 410 may maintain thelift base 12, the turntable 14 and/or the boom 40 level relative togravity. Such control of the front leveling assembly 110 and/or the rearleveling assembly 120 may be based on a mode of operation of the liftdevice 10. By way of example, the controller 410 may send and receivesignals with the turntable 14, the boom 40, the leveling system 100, thedrive system 220, the actuator circuit 300, the displacement sensors402, the roll sensors 404, the pitch sensors 406, the load sensors 408,and/or the user interface 440.

The controller 410 may be implemented as a general-purpose processor, anapplication specific integrated circuit (ASIC), one or more fieldprogrammable gate arrays (FPGAs), a digital-signal-processor (DSP),circuits containing one or more processing components, circuitry forsupporting a microprocessor, a group of processing components, or othersuitable electronic processing components. According to the exemplaryembodiment shown in FIG. 4, the controller 410 includes a processingcircuit 412 and a memory 414. The processing circuit 412 may include anASIC, one or more FPGAs, a DSP, circuits containing one or moreprocessing components, circuitry for supporting a microprocessor, agroup of processing components, or other suitable electronic processingcomponents. In some embodiments, the processing circuit 412 isconfigured to execute computer code stored in the memory 414 tofacilitate the activities described herein. The memory 414 may be anyvolatile or non-volatile computer-readable storage medium capable ofstoring data or computer code relating to the activities describedherein. According to an exemplary embodiment, the memory 414 includescomputer code modules (e.g., executable code, object code, source code,script code, machine code, etc.) configured for execution by theprocessing circuit 412. The memory 414 includes various actuationprofiles corresponding to loading conditions experienced by the levelingsystem 100 and/or corresponding to modes of operation of the lift device10, according to an exemplary embodiment. In some embodiments,controller 410 represents a collection of processing devices (e.g.,servers, data centers, etc.). In such cases, the processing circuit 412represents the collective processors of the devices, and the memory 414represents the collective storage devices of the devices.

In one embodiment, the user interface 440 includes a display and anoperator input. The display may be configured to display a graphicaluser interface, an image, an icon, and/or still other information. Inone embodiment, the display includes a graphical user interfaceconfigured to provide general information about the left device (e.g.,vehicle speed, fuel level, warning lights, battery level, etc.). Thegraphical user interface may also be configured to display a currentposition of the leveling system 100, a current position of the boom 40,a current position of the turntable 14, an orientation of the lift base12 (e.g., angle relative to a ground surface, etc.), and/or still otherinformation relating to the lift device 10 and/or the leveling system100.

The operator input may be used by an operator to provide commands to atleast one of the turntable 14, the boom 40, the leveling system 100, thedrive system 220, and the actuator circuit 300. The operator input mayinclude one or more buttons, knobs, touchscreens, switches, levers,joysticks, pedals, a steering wheel, or handles. The operator input mayfacilitate manual control of some or all aspects of the operation of thelift device 10. It should be understood that any type of display orinput controls may be implemented with the systems and methods describedherein.

According to an exemplary embodiment, the controller 410 is configuredto send and receive displacement data from the displacement sensors 402,roll data from the roll sensors 404, pitch data from the pitch sensors406, and/or load data from the load sensors 408. The displacementsensors 402 may be positioned to acquire the displacement data regardingthe front right actuator 170, the front left actuator 180, the rearright actuator 190, and/or the rear left actuator 200. The displacementdata may be indicative of an amount of displacement and/or a position(e.g., extension, retraction, etc.) of the front right actuator 170, thefront left actuator 180, the rear right actuator 190, and/or the rearleft actuator 200 (e.g., relative to a neutral position, a nominalposition, etc.). The roll sensors 404 may be positioned to acquire theroll data regarding the front leveling assembly 110, the rear levelingassembly 120, the front axle 150, and/or the rear axle 160. The rolldata may be indicative of a roll angle and/or a rate of change of theroll angle of the front axle 150 about the pin 158 and/or the rear axle160 about the corresponding pin thereof (e.g., relative to a horizontalroll alignment, a zero roll angle, etc.). The pitch sensors 406 may bepositioned to acquire the pitch data regarding the front levelingassembly 110, the rear leveling assembly 120, the front axle 150, and/orthe rear axle 160. The pitch data may be indicative of a pitch angleand/or a rate of change of the pitch angle of the front axle 150 aboutthe coupling between the chassis end 132 of the front trailing arm 130and the front end 20 of the lift base 12 and/or the rear axle 160 aboutthe coupling between the chassis end 142 of the rear trailing arm 140and the rear end 30 of the lift base 12 (e.g., relative to a horizontalpitch alignment, a zero pitch angle, etc.). The load sensors 408 may bepositioned to acquire the load data regarding the front tractiveelements 16 and/or the rear tractive elements 18. The load data may beindicative of a loading experienced by each of the front tractiveelements 16 and/or each of the rear tractive elements 18. According toan exemplary embodiment, the controller 410 monitors the levelingstatus, the ground following status, and/or the height of the lift base12 of the lift device 10 using the displacement data, the roll data, thepitch data, and/or the load data.

According to an exemplary embodiment, the controller 410 is configuredto facilitate operating the lift device in various modes of operation.The modes of operation of the lift device may include a transportationor stowed mode, a driving mode, a boom operation mode, and/or acalibration mode. The various modes of operation may be selected by anoperator of the lift device 10 and/or automatically activated by thecontroller 410 based on the current operation of the lift device 10(e.g., driving, operating the turntable 14, operating the boom 40,etc.). The controller 410 may actively control at least one of the frontleveling assembly 110 and the rear leveling assembly 120 based on themode of operation of the lift device 10. According to an exemplaryembodiment, the controller 410 is configured to control operation of thefront right actuator 170, the front left actuator 180, the rear rightactuator 190, and/or the rear left actuator 200 based on at least one ofthe displacement data, the roll data, the pitch data, the load data, themode of operation of the lift device 10, the operation of the turntable14, and/or the operation of the boom 40.

According to an exemplary embodiment, the controller 410 is configuredto provide a command to the leveling system 100 (e.g., the levelingmodules 172, 182, 192, and 202, etc.) to reduce the overall height ofthe lift base 12 to a target height (e.g., a minimum height, a stowedheight, a shipping height, etc.) in response to the lift device 10 beingswitched into the transportation or stowed mode (e.g., to provide asquatting capability, etc.). Such a reduction in the overall height ofthe lift device 10 may facilitate storing the lift device within an ISOcontainer (e.g., containerization, etc.) and/or provide greaterstability and clearance during transportation (e.g., by lowering thecenter of gravity thereof, etc.). In some embodiments, the controller410 is configured to limit the speed of the lift device 10 and/or theoperation of the turntable 14 and/or the boom 40 during thetransportation mode.

According to an exemplary embodiment, the controller 410 is configuredto provide a command to the leveling system 100 to calibrate thedisplacement sensors 402, the roll sensors 404, the pitch sensors 406,and/or the load sensors 408 when the lift device 10 is in thecalibration mode. The calibration mode may be activated each time thelift device 10 is turned on, on a periodic basis, in response to anoperator command, and/or in response to the various data indicatingpotential miscalibration. The calibration mode may include the levelingsystem 100, the turntable 14, and/or the boom 40 returning to a nominalposition (e.g., fully extended, fully retracted, etc.) such that thesensors may be zeroed out.

According to an exemplary embodiment, the controller 410 is configuredto actively control the rear leveling assembly 120 (e.g., based on thepitch data, the roll data, the displacement data, and/or the load data,etc.) and passively control the front leveling assembly 110 (e.g., asdepicted in FIG. 11, etc.) in response to the lift device 10 beingoperated in the driving mode. In other embodiments, the front levelingassembly 110 is actively controlled, while the rear leveling assembly120 is passively controlled when the lift device 10 is in the drivingmode. The passive control of the front leveling assembly 110 may allowthe front axle 150 to freely float and/or oscillate as the fronttractive elements 16 encounter various terrain (e.g., slopes, pot holes,rocks, etc.) with the front right actuator 170 and the front leftactuator 180 fluidly coupled (e.g., by the front low pressure line 340and the auxiliary line 360, etc.). In one embodiment, the front axle 150is allowed to freely float in the roll direction. In some embodiments,the front axle 150 is allowed to freely float in the roll directionand/or the pitch direction. The active control of the rear levelingassembly 120 (e.g., the rear right actuator 190, the rear left actuator200, etc.) may facilitate the controller 410 in maintaining the liftbase 12 level relative to gravity. In some embodiments, operation of theturntable 14 and/or the boom 40 are limited and/or disabled by thecontroller 410 during the driving mode. By way of example, limiting theuse of the turntable 14 and/or the boom 40 may maintain a lower centerof gravity of the lift device 10 such that the lift device 10 mayoperate at higher speeds with improved stability. According to anexemplary embodiment, the controller 410 actively controlling of therear leveling assembly 120 and passively controlling the front levelingassembly 110 provides a smooth ground following capability and increasedterrainability (e.g., terrain negotiation, etc.). The actuator circuit300 may also require less power (e.g., requires less hydraulic flow fromthe pump 302, since only the two rear actuators are actively controlled,compared to actively controlling all four actuators, etc.) during thedriving mode of the lift device 10.

According to an exemplary embodiment, the controller 410 is configuredto actively control the front leveling assembly 110 and the rearleveling assembly 120 in response to the lift device 10 being operatedin the boom operation mode (e.g., the turntable 14 and/or the boom 40being operated, etc.). The active control of the rear leveling assembly120 (e.g., the rear right actuator 190, the rear left actuator 200,etc.) and the front leveling assembly 110 (e.g., the front rightactuator 170, the front left actuator 180, etc.) may facilitate thecontroller 410 in maintaining the lift base 12 level (e.g., move level,completely level, etc.) relative to gravity. In some embodiments, thecontroller 410 limits the speed of the lift device 10 during the boomoperation mode. By way of example, operating the turntable 14 and/or theboom 40 may raise the center of gravity of the lift device 10 such thatlimiting the speed to lower operating speeds may facilitate increasedstability. According to an exemplary embodiment, the controller 410 isconfigured to control operation of the front right actuator 170, thefront left actuator 180, the rear right actuator 190, and the rear leftactuator 200 based on at least one of the displacement data, the rolldata, the pitch data, the load data, the position of the turntable 14,and/or the position of the boom 40 (e.g., the platform assembly 92,etc.) while the lift device 10 is in the boom operation mode. The boomoperation mode may be used while the lift device 10 is stationary and/ormoving (e.g., at a reduced speed, a governed speed, a creep speed,etc.). The various data may be used to maintain the lift base 12 levelrelative to gravity and/or maintain the front tractive elements 16 andthe rear tractive elements 18 in contact with the ground as the centerof gravity of the lift device 10 varies while in the boom operation mode(e.g., as the platform assembly 92 is selectively raised, lowered,extended, retracted, etc.).

According to the exemplary embodiment shown in FIGS. 13-20, the liftdevice 10 is configured to operate (e.g., as controlled by thecontroller 410, etc.) in various modes (e.g., to negotiate variousterrain or obstacles, facilitate transportation, etc.). As shown inFIGS. 13 and 14, the leveling system 100 of the lift device 10 isconfigured to increase the terrainability by increasing the capabilitiesof the lift device 10 to negotiate obstacles (e.g., pot holes, bumps,rocks, etc.), while maintaining the lift base 12, the turntable 14, andthe boom 40 level relative to gravity (e.g., while operating in thedriving mode, the boom operation mode, etc.). The leveling system 100may additionally improve traction capabilities of the lift device 10 bydistributing loads throughout the rear tractive elements 18 and/or thefront tractive elements 16 while on and/or driving along uneven and/orsloped terrain. As shown in FIGS. 15-18, the leveling system 100 isconfigured to facilitate negotiation of and self-leveling on inclines orslopes, while maintaining the lift base 12, the turntable 14, and theboom 40 level relative to gravity (e.g., while operating in the drivingmode, the boom operation mode, etc.). Such self-leveling may ease theloading of the lift device 10 onto a truck bed and/or increase thestability of the lift device 10 during operation of the boom 40 and/orthe turntable 14 while on an incline or slope. As shown in FIGS. 19 and20, the leveling system 100 is configured to facilitate a squattingcapability such that the height of the lift base 12 is reduced. Thesquatting capability may provide greater stability and clearance whilethe lift device 10 is transported (e.g., via a truck, etc.) and/orfacilitate containerization of the lift device 10 for shipping (e.g., byreducing the overall height of the lift device 10 such that the liftdevice 10 fits within an ISO container, etc.).

Referring now to FIG. 21, a method for controlling the lift device 10according to various modes of operation is shown according to anexemplary embodiment. At step 502, the lift device 10 is powered on(e.g., in response to receiving a power on command from an operator,etc.). At step 504, the controller 410 determines a mode of operation ofthe lift device 10 (e.g., transportation mode, calibration mode, drivingmode, boom operation mode, etc.). The mode of operation may be manuallyoperator selected, automatically initiated at power on, automaticallyinitiated at power off, and/or automatically initiated in response to anoperator input to drive the lift device 10, operate the turntable 14,and/or operate the boom 40. At step 510, the controller 410 isconfigured to provide a command to the leveling system 100 to adjust theheight of the lift base 12 to a target height (e.g., a transportationheight, a stowed height, etc.) in response to the initiation of atransport mode of operation. The transport mode of operation may beinitiated in response to an operator selection and/or in response to thelift device 10 being powered off. In some embodiments, the controller410 is configured to limit the speed of the lift device 10 and/or theoperation of the turntable 14 and/or the boom 40 during thetransportation mode of operation. At step 520, the controller 410 isconfigured to provide a command to the leveling system 100 to run asensor calibration algorithm to facilitate calibrating one or moresensors of the lift device 10 (e.g., the displacement sensors 402, theroll sensors 404, the pitch sensors 406, the load sensors 408, etc.) inresponse to the initiation of a calibration mode of operation. Thecalibration mode of operation may be initiated each time the lift device10 is turned on, on a periodic basis, in response to an operatorcommand, and/or in response to the various data indicating potentialmiscalibration. The sensor calibration algorithm may include theleveling system 100, the turntable 14, and/or the boom 40 returning to anominal position (e.g., fully extended, fully retracted, etc.) such thatthe sensors may be zeroed out.

At step 530, the controller 410 is configured to actively control afirst leveling assembly (e.g., the rear leveling assembly 120, etc.) andpassively control a second leveling assembly (e.g., the front levelingassembly 110, etc.) of the leveling system 100 in response to initiationof the driving mode of operation. The driving mode may be initiated inresponse to an operator providing a command to drive the lift device 10while the boom 40 is in a stowed position and/or a boom operation mode.According to an exemplary embodiment, the controller 410 is configuredto control the first leveling assembly based on data (e.g., pitch data,roll data, the displacement data, the load data, etc.) received from theone or more sensors (e.g., the displacement sensors 402, the rollsensors 404, the pitch sensors 406, the load sensors 408, etc.). In someembodiments, the controller 410 is configured to limit and/or disableoperation of the turntable 14 and/or the boom 40 while the lift device10 is in the driving mode.

At step 540, the controller 410 is configured to determine a compoundtilt angle (e.g., a combination of the roll angle and the pitch angle,etc.) of the lift device 10 and compare the compound tilt angle to afirst tilt angle threshold in response to the initiation of a boomoperation mode. The boom operation mode may be initiated in response toan operator providing a command to operate the turntable 14 and/or theboom 40 of the lift device 10. According to an exemplary embodiment, thefirst tilt angle threshold is five degrees. In other embodiments, thefirst tilt angle threshold is less than or greater than five degrees(e.g., four degrees, six degrees, seven degrees, etc.). If the compoundtilt angle is greater than the first tilt angle threshold, thecontroller 410 is configured to disable the leveling function, disablethe drive function, and/or limit boom function (step 542). If thecompound tilt angle is less than the first tilt angle threshold, thecontroller 410 is configured to compare the compound tilt angle to asecond tilt angle threshold (step 544). According to an exemplaryembodiment, the second tilt angle threshold is three degrees. In otherembodiments, the second tilt angle threshold is less than or greaterthan three degrees (e.g., four degrees, two degrees, five degrees,etc.). If the compound tilt angle is greater than the second tilt anglethreshold, but less than the first tilt angle threshold, the controller410 is configured to limit drive function (e.g., to a creep speed, areduced speed, etc.) and/or limit boom function (step 546). If thecompound tilt angle is less than the second tilt angle threshold, thecontroller 410 is configured to provide a command to actively controlthe first leveling assembly (e.g., the rear leveling assembly 120, etc.)and the second leveling assembly (e.g., the front leveling assembly 110,etc.) of the leveling system 100 (step 548). According to an exemplaryembodiment, the controller 410 is configured to control the firstleveling assembly and the second leveling assembly based on (i) data(e.g., pitch data, roll data, load data, displacement data etc.)received from the one or more sensors (e.g., the displacement sensors402, the roll sensors 404, the pitch sensors 406, the load sensors 408,etc.), (ii) the operation of the boom 40 (e.g., the position of theplatform assembly 92 relative to the lift base 12, etc.), and/or (iii)the operation of the turntable 14 (e.g., rotation thereof, etc.). Atstep 550, the controller 410 is configured to power off the lift device10 (e.g., in response to receiving a power off command from an operator,etc.). At step 552, the method 500 is concluded until a subsequent poweron command is received (step 502).

As utilized herein, the terms “approximately”, “about”, “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like, as used herein, mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent) or moveable (e.g.,removable, releasable, etc.). Such joining may be achieved with the twomembers or the two members and any additional intermediate members beingintegrally formed as a single unitary body with one another or with thetwo members or the two members and any additional intermediate membersbeing attached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” etc.) are merely used to describe the orientation ofvarious elements in the figures. It should be noted that the orientationof various elements may differ according to other exemplary embodiments,and that such variations are intended to be encompassed by the presentdisclosure.

Also, the term “or” is used in its inclusive sense (and not in itsexclusive sense) so that when used, for example, to connect a list ofelements, the term “or” means one, some, or all of the elements in thelist. Conjunctive language such as the phrase “at least one of X, Y, andZ,” unless specifically stated otherwise, is otherwise understood withthe context as used in general to convey that an item, term, etc. may beeither X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z (i.e., anycombination of X, Y, and Z). Thus, such conjunctive language is notgenerally intended to imply that certain embodiments require at leastone of X, at least one of Y, and at least one of Z to each be present,unless otherwise indicated.

It is important to note that the construction and arrangement of theelements of the systems and methods as shown in the exemplaryembodiments are illustrative only. Although only a few embodiments ofthe present disclosure have been described in detail, those skilled inthe art who review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multiple partsor elements. It should be noted that the elements and/or assemblies ofthe components described herein may be constructed from any of a widevariety of materials that provide sufficient strength or durability, inany of a wide variety of colors, textures, and combinations.Accordingly, all such modifications are intended to be included withinthe scope of the present inventions. Other substitutions, modifications,changes, and omissions may be made in the design, operating conditions,and arrangement of the preferred and other exemplary embodiments withoutdeparting from scope of the present disclosure or from the spirit of theappended claims.

The invention claimed is:
 1. A lift device, comprising: a chassis havinga front end and a rear end; a rear leveling assembly coupled to the rearend of the chassis, the rear leveling assembly including: a first rearactuator; and a second rear actuator, wherein the first rear actuatorand the second rear actuator are selectively engageable to facilitateproviding active control of a rear pitch adjustment and a rear rolladjustment of the rear leveling assembly; and a front leveling assemblycoupled to the front end of the chassis, the front leveling assemblyincluding: a first front actuator; and a second front actuator, whereinthe first front actuator and the second front actuator are (i)selectively fluidly couplable to facilitate providing passive control ofa front pitch adjustment and a front roll adjustment of the frontleveling assembly and (ii) selectively fluidly decouplable to facilitateproviding active control of the front pitch adjustment and the frontroll adjustment of the front leveling assembly.
 2. The lift device ofclaim 1, wherein each of the rear leveling assembly and the frontleveling assembly includes a carrier arm pivotally coupled to thechassis and an axle pivotally coupled to the carrier arm.
 3. The liftdevice of claim 2, wherein the carrier arm defines a carrier arm pivotinterface and the axle defines an axle pivot interface positioned toengage with the carrier arm pivot interface, the carrier arm pivotinterface and the axle pivot interface cooperatively receiving afastener to pivotally couple the axle to the carrier arm.
 4. The liftdevice of claim 3, wherein the carrier arm has: a base defining achassis pivot interface that pivotally couples the carrier arm to alower end of the chassis; a projection defining the carrier arm pivotinterface; and a transition extending angularly between the base and theprojection such that the projection is elevated relative to the base. 5.The lift device of claim 1, wherein the front leveling assembly furtherincludes one or more valves positioned to facilitate at least one of (i)selectively isolating the first front actuator and the second frontactuator from a high pressure fluid source and (ii) selectively fluidlycoupling the first front actuator to the second front actuator.
 6. Thelift device of claim 1, wherein the first front actuator and the secondfront actuator are selectively fluidly decoupled during a transport modesuch that the front leveling assembly is actively controllable toprovide the front pitch adjustment and the front roll adjustment.
 7. Thelift device of claim 6, wherein the first front actuator, the secondfront actuator, the first rear actuator, and the second rear actuatorare configured to facilitate reducing an overall height of the liftdevice to a target height in the transport mode.
 8. The lift device ofclaim 1, wherein the first front actuator and the second front actuatorare selectively fluidly decoupled during a calibration mode such thatthe front leveling assembly is actively controllable to provide thefront pitch adjustment and the front roll adjustment.
 9. The lift deviceof claim 8, wherein the first front actuator, the second front actuator,the first rear actuator, and the second rear actuator are configured tobe returned to a nominal position to facilitate establishing a referencefor a sensor of the lift device in the calibration mode.
 10. The liftdevice of claim 9, wherein the sensor includes at least one of adisplacement sensor, a roll sensor, a pitch sensor, and a load sensor.11. The lift device of claim 1, further comprising a boom pivotallycoupled to the chassis, wherein the first front actuator and the secondfront actuator are selectively fluidly decoupled during a boom operationmode such that the front leveling assembly is actively controllable toprovide the front pitch adjustment and the front roll adjustment. 12.The lift device of claim 11, wherein a speed of the lift device islimited during the boom operation mode.
 13. The lift device of claim 11,wherein the first front actuator, the second front actuator, the firstrear actuator, and the second rear actuator are configured to beactively controlled while the boom is in use in the boom operation mode.14. The lift device of claim 1, wherein the first front actuator and thesecond front actuator are selectively fluidly coupled during a drivingmode such that the front leveling assembly provides passive control ofthe front pitch adjustment and the front roll adjustment.
 15. The liftdevice of claim 14, further comprising a boom, wherein operation of theboom is limited during the driving mode.
 16. A leveling system for alift device, comprising: a first leveling assembly configured topivotally couple to a first end of a chassis of the lift device, thefirst leveling assembly including a first actuator and a secondactuator; a second leveling assembly configured to pivotally couple toan opposing second end of the chassis of the lift device, the secondleveling assembly including a third actuator and a fourth actuator;wherein the first actuator and the second actuator are configured to bepassively controlled during a first mode of operation of the liftdevice; wherein the first actuator and the second actuator areconfigured to be actively controlled during a second mode of operationof the lift device; wherein the first actuator and the second actuatorare (i) fluidly couplable to each other during the first mode ofoperation and (ii) fluidly decouplable from each other during the secondmode of operation; and wherein the third actuator and the fourthactuator are configured to be actively controlled during at least one ofthe first mode of operation and the second mode of operation of the liftdevice.
 17. The leveling system of claim 16, wherein the first levelingassembly and the second leveling assembly are configured to facilitate apitch adjustment and a roll adjustment of the chassis.
 18. A levelingsystem for a vehicle, comprising: a first leveling assembly configuredto pivotally couple to a first end of a chassis of the vehicle, whereinthe first leveling assembly is configured to be passively controlled toprovide a passive pitch adjustment and a passive roll adjustment of thefirst leveling assembly during a first mode of operation, and whereinthe first leveling assembly is configured to be actively controlled toprovide an active pitch adjustment and an active roll adjustment of thefirst leveling assembly during a second mode of operation; and a secondleveling assembly configured to pivotally couple to an opposing secondend of the chassis, wherein the second leveling assembly is configuredto be actively controlled to provide an active pitch adjustment and anactive roll adjustment of the second leveling assembly during the firstmode of operation and the second mode of operation.